Image data processing method and apparatus

1. An inverse orthogonal transform method for reconstructing an original image by quantizing the result of two-dimensional orthogonal transform on each block of image data comprising NXN picture elements, decoding input codes which are obtained by encoding, dequantizing the result, and finally performing two-dimensional inverse orthogonal transform; said inverse orthogonal transform method comprising: dividing each column of a coefficient matrix comprising N rows and N columns, a result of two-dimensional orthogonal transform on said image data block, into one-dimensional partial sequences each comprising a predetermined number of components, extracting from the one-dimensional partial sequences a one-dimensional partial sequence comprising significant coefficients, which are positioned in any position of the one-dimensional partial sequence, containing a value other than zero, performing an operation equivalent to one-dimensional orthogonal transform on each component of said extracted one-dimensional partial sequence, outputting the operation result corresponding to said extracted partial sequence as the component of a column corresponding to the result of one-dimensional inverse transform, and performing the second-dimensional orthogonal transform on the result of said one-dimensional inverse transform.

2. The inverse orthogonal transform method according to claim 1 , wherein the result of the first-dimensional inverse transform of each column is outputted as a component of a row corresponding in a transposed matrix.

3. An inverse orthogonal transform circuit of an image reconstructing apparatus for reconstructing an original image by quantizing the result of two-dimensional orthogonal transform on each block of image data comprising NXN picture elements, decoding input codes which are obtained by encoding, dequantizing the result, and finally performing two-dimensional inverse orthogonal transform; said inverse orthogonal transform circuit comprising: a coefficient storing unit storing said inputted coefficient matrix as a matrix comprising N rows and N columns with each column divided into a one-dimensional partial sequence, a read control unit comprising a determining unit determining whether or not each of one-dimensional partial sequences comprising each column of said coefficient matrix inputted in said coefficient storing unit is a significant one-dimensional partial sequence comprising significant coefficients, which are positioned in any position of the one-dimensional partial sequence, containing a value other than zero, and an address storing unit storing an address in said coefficient storing unit corresponding to the one-dimensional partial sequence which is determined to be a significant one-dimensional partial sequence, wherein said read control unit instructs, according to the address stored in said address storing unit, said coefficient storing unit to output each component contained in a significant partial sequence, a transform constant storing unit storing a constant matrix in N rows and N columns comprising transform constants corresponding to each component of said coefficient matrix and for outputting a transform constant contained in a column of a constant matrix corresponding to the component of the coefficient matrix outputted by said coefficient storing unit, a first transforming unit performing operation corresponding to the orthogonal transforming on each component of the significant one-dimensional partial sequence in an inputted coefficient matrix and transform constants outputted from said transform constant storing unit, and for outputting the operation result as the result of one-dimensional inverse transform on the corresponding column, a transform result storing unit storing the output of said first transforming unit, a write control unit designating, according to the address stored in said address storing unit, the storage position in said transform result storing unit of the result of one-dimensional inverse transform on the corresponding column in said coefficient matrix, and a second transforming unit performing the second-dimensional orthogonal transform according to the result of one-dimensional inverse transform stored in said transform result storing unit.

4. The inverse orthogonal transforming circuit according to claim 3 , wherein said coefficient storing unit has a capacity of storing a coefficient matrix corresponding to each of two said blocks, and said first transforming unit performs one-dimensional inverse transform concurrently with the input of a coefficient matrix to said coefficient storing unit.

5. An inverse orthogonal transform circuit of an image reconstructing apparatus for reconstructing an original image by quantizing the result of two-dimensional orthogonal transform on each block of image data comprising NXN picture elements, decoding input codes which are obtained by encoding, dequantizing the result, and finally performing two-dimensional inverse orthogonal transform; said inverse orthogonal transform circuit comprising: a coefficient storing unit storing each component of said inputted coefficient matrix as a matrix comprising N rows and N columns, a read control unit comprising a determining unit determining whether or not each of partial sequences comprising each column of said coefficient matrix inputted in said coefficient storing unit is a significant partial sequence comprising asignificant coefficient, and an address storing unit storing an address in said coefficient storing unit corresponding to the partial sequence which is determined to be a significant partial sequence, wherein said read control unit instructs, according to the address stored in said address storing unit, said coefficient storing unit to output each component contained in a significant partial sequence, a transform constant storing unit storing a constant matrix in N rows and N columns comprising transform constants corresponding to each component of said coefficient matrix and for outputting a transform constant contained in a column of a constant matrix corresponding to the component of the coefficient matrix outputted by said coefficient storing unit, a first transforming unit performing operation corresponding to the orthogonal transforming on each component in an inputted coefficient matrix and transform constants outputted from said transform constant storing unit, and for outputting the operation result as the result of one-dimensional inverse transform on the corresponding column, a transform result storing unit storing the output of said first transforming unit, a write control unit designating, according to the address stored in said address storing unit, the storage position in said transform result storing unit of the result of one-dimensional inverse transform on the corresponding column in said coefficient matrix, and a second transforming unit performing the second-dimensional orthogonal transform according to the result of one-dimensional inverse transform stored in said transform result storing unit, and wherein said determining unit determines whether or not a partial sequence comprising N/2 components is a significant partial sequence, said transform constant storing unit alternately outputs the first N/2 transform constants of the corresponding column and the last N/2 transform constants according to the output of each component of said coefficient matrix, said first transforming unit comprises N/2 operating unit each corresponding to N/2 transform constants simultaneously outputted by said transform constant storing unit, and said N/2 operating unit comprises a multiplying unit multiplying a component of an inputted coefficient matrix by each of transform constants alternately outputted from said transform constant storing unit according to said component, an accumulating unit accumulating each of the results of multiplication obtained alternately by said multiplying unit, and a storing unit storing each of the accumulation results obtained by said accumulating unit.

6. The inverse orthogonal transforming circuit according to claim 5 , wherein said first transforming unit comprises an operation control unit controlling the execution number of operations by said multiplying unit and said accumulating unit according to the address of a significant partial sequence contained in each column in said coefficient matrix stored in said address storing unit.

7. The inverse orthogonal transforming circuit according to claim 3 , wherein said write control unit comprises an address generating unit generating, according to the operation result obtained by said first transforming unit, an address in said transform result storing unit the row in the transposed matrix where a matrix comprising the results of said one-dimensional inverse transform is transposed.

8. The inverse orthogonal transforming circuit according to claim 7 comprising: a detecting unit detecting a significant coefficient other than zero in each component of the inputted results of said one-dimensional inverse transform, and an output instructing unit instructing, according to the detection result of said detecting unit, said detecting unit to output a partial sequence including a significant coefficient in each column of a resultant matrix of said one-dimensional inverse transform, wherein said second transforming unit performs the second-dimensional orthogonal transform on a partial sequence outputted by said transform result storing unit.

9. The inverse orthogonal transforming circuit according to claim 7 comprising an input unit, instead of said second transforming unit, for inputting the result of one-dimensional inverse transform stored in said transform result storing unit to said first transforming unit, and for instructing said transform constant storing unit to output a corresponding transform constant.

10. The inverse orthogonal transforming circuit according to claim 9 comprising: a detecting unit detecting a significant coefficient other than zero in each component of the results of said one-dimensional inverse transform inputted in said transform result storing unit, and an output instructing unit instructing, according to the detection result of said detecting unit, said transform result storing unit to output a partial sequence including a significant coefficient among each column of a resultant matrix of said one-dimensional inverse transform, wherein said input unit inputs a partial sequence outputted by said transform result storing unit to said first transforming unit.

11. An inverse orthogonal transform circuit of an image reconstructing apparatus for reconstructing an original image by quantizing the result of two-dimensional orthogonal transform on each block of image data comprising NXN picture elements, decoding input codes which are obtained by encoding, dequantizing the result, and finally performing two-dimensional inverse orthogonal transform; said inverse orthogonal transform circuit comprising: a coefficient storing means for storing each component of said inputted coefficient matrix as a matrix comprising N rows and N columns, a read control means comprising a determining means for determining whether or not a one of one-dimensional partial sequences comprising each column of said coefficient matrix inputted in said coefficient storing means is a significant one-dimensional partial sequence comprising significant coefficients, which are positioned in any position of the one-dimensional partial sequence, not indicating zero as a result of a quantization, and an address storing means for storing an address in said coefficient storing means corresponding to the partial sequence which is determined to be a significant partial sequence, wherein said read control means instructs, according to the address stored in said address storing means, said coefficient storing means to output each component contained in a significant partial sequence, transform constant storing means for storing a constant matrix in N rows and N columns comprising transform constants corresponding to each component of said coefficient matrix and for outputting a transform constant contained in a column of a constant matrix corresponding to the component of the coefficient matrix outputted by said coefficient storing means, first transforming means for performing an operation corresponding to a one-dimensional orthogonal transform on each component of said significant one-dimensional partial sequence in an inputted coefficient matrix and outputting the operation result as the result of one-dimensional inverse transform on the corresponding column, transform result storing means for storing the output of said first transforming means, write control means for designating, according to the address stored in said address storing means, the storage position in said transform result storing means of the result of one-dimensional inverse transform on the corresponding column in said coefficient matrix, and second transforming means for performing the second-dimensional orthogonal transform according to the result of one-dimensional transform stored in said transform result storing means.

12. A computer-readable storage medium which records a program for enabling a computer to perform an inverse orthogonal transform method for reconstructing an original image by quantizing a result of two-dimensional orthogonal transform on each block of image data comprising NXN picture elements, decoding input codes which are obtained by encoding, dequantizing the result, and finally performing two-dimensional inverse orthogonal transform; the program enabling the computer to perform: dividing each column of a coefficient matrix comprising N rows and N columns, a result of two-dimensional orthogonal transform on said image data block, into one-dimensional partial sequences each comprising a predetermined number of components, extracting from the one-dimensional partial sequences a one-dimensional partial sequence comprising significant coefficients, which are positioned in any position of the one-dimensional partial sequence, containing a value other than zero obtained by a quantization, performing operation equivalent to one-dimensional orthogonal transform on each component of said extracted one-dimensional partial sequence, outputting the operation result corresponding to said extracted partial sequence as the component of a column corresponding to the result of one-dimensional inverse transform, and performing the second-dimensional orthogonal transform on the result of said one-dimensional inverse transform.